mcp-router CLI before 0.6.3 Binds the MCP Aggregator to All Interfaces Without Requiring Authentication
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-306.
Summary
The mcp-router CLI served its MCP aggregator on every interface and enforced authentication only when the operator asked for it. The serve command in apps/cli/src/commands/serve.ts defaulted its host to the all-interfaces address on a fixed port, and required a token only when the corresponding flag was supplied, so a default invocation exposed the aggregator, and every MCP server it fronted, to anyone able to reach the port. Release 0.6.3 defaults the host to the loopback address and refuses to start without a token whenever the host it is given is not a loopback address; no earlier release carries either check.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| mcp-router | mcp-router | before 0.6.3 | 0.6.3 | Patch available | CNA |
- mcp-router Vendormcp-router Affected before 0.6.3 Fixed in 0.6.3 Patch available CNA
Remediation
- Fix · CNA mcp-router (mcp-router) Fixed in 0.6.3
Timeline
- 2026-10-02 Threatist record created from CVE-2026-81094
- 2026-10-03 Alias added: GHSA-g448-x63h-m2m3
References
Sources
- CVE-2026-81094 · CVE Program
- CVE-2026-81094 · NVD
- FIRST EPSS
- GHSA-g448-x63h-m2m3 · GitHub Advisory Database · CC BY 4.0
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